Concordance of Sputum and Feces Samples for Detecting Mycobacterium Tuberculosis using Xpert® MTB/RIF Ultra

Introduction: Tuberculosis (TB) remains a disease with high morbidity and mortality worldwide, and Indonesia ranks among the countries with the highest TB prevalence. There is a need to develop improved detection tools and explore alternative sample sources beyond sputum. Feces samples are one such non-sputum alternative. Xpert® MTB/RIF Ultra is a novel diagnostic tool used in Indonesia. This study aims to assess the concordance of both sputum and feces samples in detecting Mycobacterium tuberculosis (MTB) using Xpert® MTB/RIF Ultra. Methods: An analytical observational study with a cross-sectional design was conducted on TB subjects at Dr. Soetomo Regional Public Hospital (RSUD Dr. Soetomo), Surabaya, and several community health centers (puskesmas) in Surabaya. Sputum and feces samples were collected from the same subjects. These subjects underwent Feces acid-fast bacilli (AFB) tests, sputum and Feces Xpert® MTB/RIF Ultra tests, and sputum culture tests (considered the gold standard), as well as rifampicin resistance tests for positive cultures. Sensitivity and positive predictive value (PPV) tests were conducted using Medcalc software, and the concordance test employed the Kappa value. Results: The study involved 71 research subjects. The sensitivity of Feces AFB tests, sputum, and Feces Xpert® MTB/RIF Ultra tests was 7.3%, 97.6%, and 97.6%, respectively. The Cohen's Kappa consistency test for Feces AFB tests and sputum culture produced a Kappa value of 0.063 (p > 0.05). The Cohen's Kappa consistency test on sputum and Feces Xpert® MTB/RIF Ultra tests yielded a Kappa value of 0.409 (p < 0.05). The Cohen's Kappa consistency test on sputum and Feces Xpert® MTB/RIF Ultra tests compared with the rifampicin resistance tests resulted in Kappa values of 0.902 and 0.951 (p < 0.05). The CT value of Feces Xpert® MTB/RIF Ultra tests was higher than that of sputum Xpert® MTB/RIF Ultra tests. Conclusion: A concordance exists between the results of sputum and Feces Xpert® MTB/RIF Ultra tests, but no concordance is observed between the results of Feces AFB tests and sputum culture tests. The higher CT value of Feces Xpert® MTB/RIF Ultra tests compared to sputum Xpert® MTB/RIF Ultra tests indicates a lower bacterial load in feces. Feces can be considered a viable alternative sample to sputum for MTB detection using Xpert® MTB/RIF Ultra.